Panel audio loudspeaker electromagnetic actuator

ABSTRACT

An electromagnetic actuator includes an inner magnet arranged relative to an axis, an outer magnet arranged a radial distance from the axis, an inner radial wall of the outer magnet facing an outer radial wall of the inner magnet, the inner and outer radial walls being separated by an air gap, a voice coil arranged in the air gap separating the inner and outer magnets, and an actuator coupling plate attached to the voice coil. During operation of the device electrical activation of the voice coil causes axial motion of the actuator coupling plate.

CROSS-REFERENCE TO RELATED APPLICATIONS

This claims priority to Provisional Application No. 62/633,033, entitled“PANEL AUDIO LOUDSPEAKER ELECTROMAGNETIC ACTUATOR,” filed on Feb. 20,2018, and to Provisional Application No. 62/654,173, entitled“DISTRIBUTED MODE LOUDSPEAKER ELECTROMAGNETIC ACTUATOR WITH AXIALLY &RADIALLY MAGNETIZED CIRCUIT,” filed on Apr. 6, 2018, the entire contentsboth of which are incorporated herein by reference in their entirety.

BACKGROUND

Many conventional loudspeakers produce sound by inducing piston-likemotion in a diaphragm. Panel audio loudspeakers, such as distributedmode loudspeakers (DMLs), in contrast, operate by inducing uniformlydistributed vibration modes in a panel through an electro-acousticactuator. Typically, the actuators are electromagnetic or piezoelectricactuators.

SUMMARY

In general, in one aspect, the disclosure features a device including aninner magnet arranged relative to an axis, an outer magnet arranged aradial distance from the axis, an inner radial wall of the outer magnetfacing an outer radial wall of the inner magnet, the inner and outerradial walls being separated by an air gap, a voice coil arranged in theair gap separating the inner and outer magnets, and an actuator couplingplate attached to the voice coil. During operation of the deviceelectrical activation of the voice coil causes axial motion of theactuator coupling plate.

Implementations of the device can include one or more of the followingfeatures. For example, the inner and outer magnets can be axiallymagnetized or radially magnetized. In some embodiments, the inner magnetis magnetized axially and the outer magnet is magnetized radially.

The inner and outer magnets can be symmetric with respect to axialrotations.

The device can include a soft magnetic material attached to the innerand outer magnets. For example, the device can include plates onopposing sides of the inner and outer magnets in the axial directioncomprising the soft magnetic material. In some embodiments, the deviceincludes a yoke composed of the soft magnetic material.

The device can have a maximum dimension in the axial direction of 10 mmor less (e.g., 8 mm or less, 5 mm or less, 4 mm or less, 3 mm or less).

In a further aspect, the disclosure features a panel audio loudspeaker,including the device and a panel mechanically attached to the actuatorcoupling plate. The panel can include a display panel (e.g., an OLED orLCD display panel). The panel can include a touch panel. The device canbe configured to generate audio and/or haptic responses.

In a further aspect, the disclosure features a mobile device includingthe panel audio loudspeaker. The mobile device can be a mobile phone ora tablet computer. In some embodiments, the mobile device is a wearabledevice.

Among other advantages, embodiments feature electromagnetic actuatorswith compact form factors and high force output. For example, use ofconcentric axially magnetized magnets can allow for maximizing andbalancing the flux density experienced at both the inner and outer facesof a magnetic air gap in an electromagnetic actuator, maximizing a totalflux density present in the air gap and therefore maximizing the forceoutput. Such configurations may be realized in relatively small formfactors, such as actuators that may be incorporated into mobile devices.

Accordingly, embodiments may solve challenges associated with creating apanel audio loudspeaker (alternatively referred to as a distributed modeloudspeaker (DML)) within a limited physical space with sufficient forceover a prescribed audio bandwidth capable of exciting vibrational modeswithin a diaphragm while still fitting within a sufficiently smallpackage size.

Other advantages will be evident from the description, drawings, andclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an embodiment of a mobile device.

FIG. 2 is a schematic cross-sectional view of the mobile device of FIG.1.

FIG. 3A is a cross-sectional view of an embodiment of a distributed modeloudspeaker (DML) axially magnetized circuit actuator.

FIG. 3B is a sectional isometric view of the embodiment of the DML shownin FIG. 3A.

FIG. 3C is an exploded isometric view of the embodiment of the DML shownin FIG. 3A.

FIG. 4 is a plot showing a characteristic actuator force as a functionof frequency.

FIG. 5 is a cross-sectional view of another embodiment of a DML circuitactuator.

FIG. 6A is a cross-sectional view of an embodiment of a DML radiallymagnetized circuit actuator.

FIG. 6B is a sectional isometric view of the embodiment of the DML shownin FIG. 6A.

FIG. 6C is an exploded isometric view of the embodiment of the DML shownin FIG. 6A.

FIG. 7A is a cross-sectional view of an embodiment of a DMLaxially/radially magnetized circuit actuator.

FIG. 7B is a sectional isometric view of the embodiment of the DML shownin FIG. 7A.

FIG. 7C is an exploded isometric view of the embodiment of the DML shownin FIG. 7A.

FIG. 8A is a cross-sectional view of a further embodiment of a DMLcircuit actuator.

FIG. 8B is a sectional isometric view of the embodiment of the DML shownin FIG. 8A.

FIG. 9 is a schematic diagram of an embodiment of an electronic controlmodule for a mobile device.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

The disclosure features actuators for panel audio loudspeakers, such asdistributed mode loudspeakers (DMLs). Such loudspeakers can beintegrated into a mobile device, such as a mobile phone. For example,referring to FIG. 1, a mobile device 100 includes a device chassis 102and a touch panel display 104 including a flat panel display (e.g., anOLED or LCD display panel) that integrates a panel audio loudspeaker.Mobile device 100 interfaces with a user in a variety of ways, includingby displaying images and receiving touch input via touch panel display104. Typically, a mobile device has a depth of approximately 10 mm orless, a width of 60 mm to 80 mm (e.g., 68 mm to 72 mm), and a height of100 mm to 160 mm (e.g., 138 mm to 144 mm).

Mobile device 100 also produces audio output. The audio output isgenerated using a panel audio loudspeaker that creates sound by causingthe flat panel display to vibrate. The display panel is coupled to anactuator, such as a distributed mode actuator, or DMA. The actuator is amovable component arranged to provide a force to a panel, such as touchpanel display 104, causing the panel to vibrate. The vibrating panelgenerates human-audible sound waves, e.g., in the range of 20 Hz to 20kHz.

In addition to producing sound output, mobile device 100 can alsoproduces haptic output using the actuator. For example, the hapticoutput can correspond to vibrations in the range of 180 Hz to 300 Hz.

FIG. 1 also shows a dashed line that corresponds to the cross-sectionaldirection shown in FIG. 2. Referring to FIG. 2, a cross-section 200 ofmobile device 100 illustrates device chassis 102 and touch panel display104. FIG. 2 also includes a Cartesian coordinate system with X, Y, and Zaxes, for ease of reference. Device chassis 102 has a depth measuredalong the Z-direction and a width measured along the X-direction. Devicechassis 102 also has a back panel, which is formed by the portion ofdevice chassis 102 that extends primarily in the X-Y-plane. Mobiledevice 100 includes an electromagnet actuator 210, which is housedbehind display 104 in chassis 102 and affixed to the back side ofdisplay 104. Generally, electromagnet actuator 210 is sized to fitwithin a volume constrained by other components housed in the chassis,including an electronic control module 220 and a battery 230.

Referring to FIGS. 3A-3C, an embodiment of an electromagnet actuator 300is shown in a cross-sectional, a sectional isometric, and an explodedisometric view, respectively. Actuator 300 includes a pair of axiallymagnetized magnets, specifically, an inner axially magnetized magnet 370and an outer axially magnetized magnet 380, separated by an air gap 330.An axially magnetized magnet is one for which the magnetic flux lines atthe magnet's surface are aligned parallel to the z-axis for theco-ordinate system shown in FIGS. 3A-3C. In other words, the magnet'spoles are oriented along the z-axis. Inner and outer magnets 370 and 380are arranged with their magnetic poles in opposite directions. In otherwords, if magnet 370 has its north pole facing in the +z direction, thenmagnet 380 has its north pole facing in the −z direction.

In general, the magnets can be formed from a material than can bepermanently magnetized, such as rare earth magnet materials. Exemplarymaterials include neodymium iron boron, samarium cobalt, barium ferrite,and strontium ferrite.

A voice-coil 320, including voice coil windings 340, is located in airgap 330 between inner and outer soft magnetic plates 350 and 360connected, via an actuator coupling plate 310, to a diaphragm (e.g.,display 104) to generate a constant force to the diaphragm in order toexcite multiple vibrational modes of said diaphragm, e.g., to generateboth acoustic output and haptic feedback. Voice-coil 320 is sited in airgap 330 and is mechanically connected to the diaphragm to impart theforce created by the actuator to the diaphragm. Specifically, an ACsignal to voice-coil windings 340 present with an axial magnetic fieldfrom the coil which generates a force on actuator 300 to displace itback and forth in the axial (i.e., z) direction.

Soft magnetic plates (inner top plate 350, outer top plate 360, and backplate 390) sandwich axially magnetized magnets 370 and 380. Softmagnetic plates 350, 360 and 390 can be formed from a material ormaterials that are readily magnetized in the presence of an externalmagnetic field. Typically, such materials have high magneticpermeability. Examples include high carbon steel and vanadium permendur.Accordingly, soft magnetic plates 350, 360 and 390 serve to guide themagnetic flux lines from axially magnetized magnets 370 and 380 acrossair gap 330.

Actuator coupling plate 310 is coupled to the magnet assembly composedof magnets 350 and 360, top plates 350 and 360, and back plate 390 byone or more suspension element (not shown) that may take variousgeometric forms to provide a desired stiffness in order to tune thefundamental resonance (Fo) of the actuator to a desired frequency. Thematerial used for this suspension may be a polymer, metal or hybridmaterial.

The use of concentric axially magnetized magnets can provide increasedmagnetic field flux and/or increased uniformity in magnetic flux densityacross the entire air gap compared with actuators that simply feature asingle magnet circuit topology. Accordingly, actuators with concentricaxial magnets can provide increased force output compared to otherdesigns.

The actuator shown in FIGS. 3A-3C can be compact. For example, thethickness of the actuator in the axial direction can be on the order ofa few mm, e.g., 5 mm or less, 4 mm or less, 3 mm or less, 2 mm or less.The lateral dimensions can also be relatively small. For example, theouter axially magnetized magnet can have a lateral diameter (i.e., thediameter orthogonal to the symmetry axis) of 20 mm or less (e.g., 15 mmor less, 12 mm or less, 10 mm or less, 8 mm or less, 7 mm or less, 6 mmor less, 5 mm or less). In implementations where actuator 300 is for usein a mobile device, such as mobile phone 100, the actuator can be sizedand shaped to fit within the available space in the device chassis alongwith other components of the device.

An exemplary force vs. frequency characteristic for actuator 300 isshown in the plot in FIG. 4. Here, the vertical axis shows a magnitudeof force, while the horizontal axis shows frequency from 100 Hz to 20kHz. Both axes are shown with logarithmic scales. The actuator forcepeaks at a resonance frequency, F0, in this case at about 200 Hz. Athigher frequencies, e.g., 500 Hz to 5 kHz in the example shown, theforce v. frequency response is relatively constant. At higherfrequencies (e.g., 10 kHz to 20 kHz), the force factor monotonicallydecreases as the voice coil inductance increasingly influences theresponse.

Actuators, such as actuator 300, may be designed to specify theactuator/diaphragm fundamental resonance frequency at such a bandwidthoptimized to provide haptic feedback and a constant force bandwidth.

FIG. 5 shows another panel audio loudspeaker magnet actuator 500 thatdoes not feature a pair of axially magnetized magnets. Rather, actuator500 includes a single axially-magnetized magnet 570, which sits within asoft magnetic cup 590. Actuator 500 also includes a voice coil 520 withvoice coil windings 540 that are located in an air gap 530 between poleplate 550 and cup 590. Voice coil 520 is attached to a coupling plate510. Coupling plate 510 includes posts 580 to which one or moresuspension elements (not shown) are used to connect coupling plate 510to cup 590. A top plate 550, formed from a soft magnetic material, islocated on the top surface of magnet 570. Such systems may haveperformance limitations arising from the soft magnetic top plate 550 andcup 590 increasing inductance and electrical impedance with increasingfrequency. This increase in electrical inductance can reduce theacoustic output at high frequency.

The temperature and electrical resistance of the voice coil conductorcan also increase with increasing current which causes power compressionand limits the maximum force generated by the actuator. It is thereforeoften desirable to maximize (or at least, increase) the efficiency ofthe force generated by the actuator.

When the package size of an actuator is limited, the use of a thinmagnet disc is often used in conjunction with a ferrous cup and polepiece (such as illustrated in FIG. 5, in which actuator 500 features cup590 and top plate 550). However, this topology is often limited in itsforce generation due to the reduced flux density experienced at theouter face of the air gap compared to the flux density experienced atthe inner face of the air gap created by the pole piece. This reducesthe total flux density present in the air gap which corresponds to areduction in force output.

While the foregoing embodiments feature axially-magnetized magnets, insome embodiments, actuators can utilize radially magnetized magnets. Insuch actuators, the magnets are magnetized such that the magnetic fieldlines at the magnet's surface extend in a radial direction (i.e.,parallel to the x-y plane) relative to the vertical z-axis of theactuator at the magnet surfaces.

Referring to FIGS. 6A to 6C, an example of an actuator 600 with radiallymagnetized magnets is shown in cross-sectional, sectional isometric, andexploded isometric views, respectively. Actuator 600 includes an innerradially-magnetized magnet 670 and an outer radially-magnetized magnet680 both centered on a vertical axis and separated by an air gap 630 inwhich voice coil windings 640 of a voice coil 620 are placed. In thecurrent embodiment, a soft magnetic yoke 690 provides a frame to whichmagnets 670 and 680 are attached. An actuator coupling plate 610 (forattaching to a load, such as a flat panel display) is attached to voicecoil 620. Actuator 600 can also include one or more suspension elements(not shown) connecting yoke 690 to coupling plate 610.

The use of a concentric, radially magnetized actuator (e.g., as shown inFIGS. 6A-6C) creates a relatively long magnetic air gap which may allowa comparatively smaller length voice coil windings to be situated withinthe magnetic air gap such that the magnetic field experienced by thevoice coil and therefore the force generated would be linear andconstant. The exclusion of soft magnetic material facing and over thelength the air gap can reduce the electrical inductance and/or linearizethe electrical inductance of the voice coil compared to an equivalentmagnetic circuit that has soft magnetic material facing and over thelength of the air gap. The use of concentric radial magnets can be usedto maximize and balance the flux density experienced at both the innerand outer faces. Accordingly, such as design can increase (e.g.,maximize) the total flux density present in the air gap and thereforeincrease (e.g., maximize) the force output.

In some embodiments, electromagnetic actuators combine an axiallymagnetized magnet within an annular radially magnetized wall. It isbelieved that such actuators are able to produce more power per physicalsize and mass than conventional actuators. This increased power isbelieved to be made possible by combining, for example, both a thin,flat axially magnetized neodymium magnet and a thin wall radiallymagnetized magnet(s).

FIGS. 7A-7C depict an example of such an actuator in cross-sectional,sectional isometric, and exploded isometric views, respectively.Specifically, FIGS. 7A-7C show an actuator 700 that includes an axiallymagnetized disc magnet 760, a radially magnetized cylindrical magnet 770and a voice-coil 720 located in a magnetic air gap 730 between theradial magnet 770 and top plate 780. Actuator 700 also includes a softmagnetic top plate 780 and a soft magnetic yoke 750. The soft magnetictop plate 780 and yoke 750 serve to guide the magnetic flux lines fromthe axially magnetized magnet 760 across air gap 730. Voice coil 720 isconnected to an actuator coupling plate 710 to generate a constant forceto a diaphragm attached to plate 710 in order to excite multiplevibrational modes of said diaphragm to generate both acoustic output andhaptic feedback. Actuator 700 can also include one or more suspensionelements (not shown) connecting yoke 750 to coupling plate 710.

The magnets can be formed from a material than can be permanentlymagnetized, such as rare earth magnet materials. Exemplary materialsinclude neodymium iron boron, samarium cobalt, barium ferrite, andstrontium ferrite.

The use of both an axially magnetized and radially magnetized magnetsprovides a way to increase (e.g., maximize) and balance the flux densityexperienced at both the inner and outer faces of the soft magnetic topplate and yoke maximizing the total flux density present in the air gapand to therefore optimize (e.g., maximize) the force output.

In some embodiments, radially magnetized magnet 770 can be realized byarc segments of a magnetic material constructed in such a way to createa continuous cylinder.

The use of a complementary radially magnetized magnet surrounding theoutside of the voice coil and contained by a soft magnetic yoke containsthe magnetic flux within the structure of the magnetic motor circuitminimizing leakage of magnetic flux from the magnetic circuit therebyminimizing interactance of the electromagnetic field with othersensitive components that may be in close proximity to theelectromagnetic actuator. Additionally, the extended vertical length ofthe radially magnetized magnet provides a consistent field strength overthe full length of the mechanical excursion capability of the voicecoil.

While the components of the actuators described above are axisymmetric(e.g., composed of continuously rotationally symmetric components, suchas annular discs and the like), other implementations are also possible.For example, in some embodiments, the actuators can have elliptical orpolygonal footprints. For example, a magnetic circuit topology within anelongated (e.g., oblong) package as shown in FIGS. 8A and 8B, which showa cross-sectional and a sectional isometric view of an actuator 800.Here, actuator 800 includes an inner axially magnetized magnet 870shaped to be concentrically slightly smaller than a corresponding softmagnetic top plate 850 that is also shaped to be concentrically slightlysmaller than a corresponding voice coil 820 with voice coil windings840. A radially magnetized outer magnet 880 is separated from innermagnet 870 by an air gap 830, within which voice coil 820 sits. Outermagnet 880 can be constructed, for example, from linear magnetic blocksthat would be situated along the outer, linear sides of the voice coil.Actuator 800 further includes a soft magnetic yoke 860 and a couplingplate 810, which is attached to voice coil 820.

In general, the disclosed actuators are controlled by an electroniccontrol module, e.g., electronic control module 220 in FIG. 2 above. Ingeneral, electronic control modules are composed of one or moreelectronic components that receive input from one or more sensors and/orsignal receivers of the mobile phone, process the input, and generateand deliver signal waveforms that cause actuator 210 to provide asuitable haptic response. Referring to FIG. 9, an exemplary electroniccontrol module 900 of a mobile device, such as mobile phone 100,includes a processor 910, memory 920, a display driver 930, a signalgenerator 940, an input/output (I/O) module 950, and anetwork/communications module 960. These components are in electricalcommunication with one another (e.g., via a signal bus) and withactuator 210.

Processor 910 may be implemented as any electronic device capable ofprocessing, receiving, or transmitting data or instructions. Forexample, processor 910 can be a microprocessor, a central processingunit (CPU), an application-specific integrated circuit (ASIC), a digitalsignal processor (DSP), or combinations of such devices.

Memory 920 has various instructions, computer programs or other datastored thereon. The instructions or computer programs may be configuredto perform one or more of the operations or functions described withrespect to the mobile device. For example, the instructions may beconfigured to control or coordinate the operation of the device'sdisplay via display driver 930, waveform generator 940, one or morecomponents of I/O module 950, one or more communication channelsaccessible via network/communications module 960, one or more sensors(e.g., biometric sensors, temperature sensors, accelerometers, opticalsensors, barometric sensors, moisture sensors and so on), and/oractuator 210.

Signal generator 940 is configured to produce AC waveforms of varyingamplitudes, frequency, and/or pulse profiles suitable for actuator 210and producing acoustic and/or haptic responses via the actuator.Although depicted as a separate component, in some embodiments, signalgenerator 940 can be part of processor 910.

Memory 920 can store electronic data that can be used by the mobiledevice. For example, memory 920 can store electrical data or contentsuch as, for example, audio and video files, documents and applications,device settings and user preferences, timing and control signals or datafor the various modules, data structures or databases, and so on. Memory920 may also store instructions for recreating the various types ofwaveforms that may be used by signal generator 940 to generate signalsfor actuator 210. Memory 920 may be any type of memory such as, forexample, random access memory, read-only memory, Flash memory, removablememory, or other types of storage elements, or combinations of suchdevices.

As briefly discussed above, electronic control module 900 may includevarious input and output components represented in FIG. 9 as I/O module950. Although the components of I/O module 950 are represented as asingle item in FIG. 9, the mobile device may include a number ofdifferent input components, including buttons, microphones, switches,and dials for accepting user input. In some embodiments, the componentsof I/O module 950 may include one or more touch sensor and/or forcesensors. For example, the mobile device's display may include one ormore touch sensors and/or one or more force sensors that enable a userto provide input to the mobile device.

Each of the components of I/O module 950 may include specializedcircuitry for generating signals or data. In some cases, the componentsmay produce or provide feedback for application-specific input thatcorresponds to a prompt or user interface object presented on thedisplay.

As noted above, network/communications module 960 includes one or morecommunication channels. These communication channels can include one ormore wireless interfaces that provide communications between processor910 and an external device or other electronic device. In general, thecommunication channels may be configured to transmit and receive dataand/or signals that may be interpreted by instructions executed onprocessor 910. In some cases, the external device is part of an externalcommunication network that is configured to exchange data with otherdevices. Generally, the wireless interface may include, withoutlimitation, radio frequency, optical, acoustic, and/or magnetic signalsand may be configured to operate over a wireless interface or protocol.Example wireless interfaces include radio frequency cellular interfaces,fiber optic interfaces, acoustic interfaces, Bluetooth interfaces, NearField Communication interfaces, infrared interfaces, USB interfaces,Wi-Fi interfaces, TCP/IP interfaces, network communications interfaces,or any conventional communication interfaces.

In some implementations, one or more of the communication channels ofnetwork/communications module 960 may include a wireless communicationchannel between the mobile device and another device, such as anothermobile phone, tablet, computer, or the like. In some cases, output,audio output, haptic output or visual display elements may betransmitted directly to the other device for output. For example, anaudible alert or visual warning may be transmitted from the electronicdevice 100 to a mobile phone for output on that device and vice versa.Similarly, the network/communications module 960 may be configured toreceive input provided on another device to control the mobile device.For example, an audible alert, visual notification, or haptic alert (orinstructions therefor) may be transmitted from the external device tothe mobile device for presentation.

The actuator technology disclosed herein can be used in panel audiosystems, e.g., designed to provide acoustic and/or haptic feedback. Thepanel may be a display system, for example based on OLED of LCDtechnology. The panel may be part of a smartphone, tablet computer, orwearable devices (e.g., smartwatch or head-mounted device, such as smartglasses).

Other embodiments are in the following claims.

What is claimed is:
 1. A device, comprising: an inner magnet arrangedrelative to an axis; an outer magnet arranged a radial distance from theaxis, an inner radial wall of the outer magnet facing an outer radialwall of the inner magnet, the inner and outer radial walls beingseparated by an air gap; a voice coil arranged in the air gap separatingthe inner and outer magnets; and an actuator coupling plate attached tothe voice coil, wherein during operation of the device electricalactivation of the voice coil causes axial motion of the actuatorcoupling plate.
 2. The device of claim 1, wherein the inner and outermagnets are axially magnetized.
 3. The device of claim 1, wherein theinner and outer magnets are radially magnetized.
 4. The device of claim1, wherein the inner magnet is axially magnetized and the outer magnetis radially magnetized.
 5. The device of claim 1, wherein the inner andouter magnets are symmetric with respect to axial rotations.
 6. Thedevice of claim 1, further comprising a soft magnetic material attachedto the inner and outer magnets.
 7. The device of claim 6, furthercomprising plates on opposing sides of the inner and outer magnets inthe axial direction comprising the soft magnetic material.
 8. The deviceof claim 6, further comprising a yoke comprising the soft magneticmaterial.
 9. The device of claim 1, wherein the device has a maximumdimension in the axial direction of 10 mm or less.
 10. A panel audioloudspeaker, comprising the device of claim 1 and a panel mechanicallyattached to the actuator coupling plate.
 11. The panel audio loudspeakerof claim 10, wherein the panel comprises a display panel.
 12. The panelaudio loudspeaker of claim 10, wherein the panel comprises a touchpanel.
 13. The panel audio loudspeaker of claim 10, wherein the deviceis configured to generate audio and/or haptic responses.
 14. A mobiledevice, comprising: a device chassis; an electronic display panelattached to the device chassis; an actuator housed within the devicechassis, the actuator comprising: an inner magnet arranged relative toan axis; an outer magnet arranged a radial distance from the axis, aninner radial wall of the outer magnet facing an outer radial wall of theinner magnet, the inner and outer radial walls being separated by an airgap; a voice coil arranged in the air gap separating the inner and outermagnets; and an actuator coupling plate attached to the voice coil andto the electronic display panel; and an electronic control modulecomprising a processor and housed within the device chassis, theelectronic control module being programmed to electrically activate thevoice coil to cause axial motion of the actuator coupling plate.
 15. Themobile device of claim 14, wherein the mobile device is a mobile phoneor a tablet computer.
 16. A wearable device, comprising: a devicechassis; a panel attached to the device chassis; an actuator housedwithin the device chassis, the actuator comprising: an inner magnetarranged relative to an axis; an outer magnet arranged a radial distancefrom the axis, an inner radial wall of the outer magnet facing an outerradial wall of the inner magnet, the inner and outer radial walls beingseparated by an air gap; a voice coil arranged in the air gap separatingthe inner and outer magnets; and an actuator coupling plate attached tothe voice coil and to the panel; and an electronic control modulecomprising a processor and housed within the device chassis, theelectronic control module being programmed to electrically activate thevoice coil to cause axial motion of the actuator coupling plate.
 17. Thewearable device of claim 16, wherein the wearable device is a smartwatch or a head-mounted device